track-video-transition: update for videomixer pad template name change
track-video-transition: update for videomixer pad template name change

pitivi/gst-editing-services,cfoch/gst-editing-services,volodymyrrudyi/gst-editing-services,volodymyrrudyi/gst-editing-services,cfoch/ges,cfoch/ges,cfoch/ges,volodymyrrudyi/gst-editing-services,cfoch/ges,cfoch/gst-editing-services,cfoch/gst-editing-services,pitivi/gst-editing-services,pitivi/gst-editing-services,pitivi/gst-editing-services,cfoch/gst-editing-services